The present invention relates to a hydraulic controller used for a transmission which comprises an oil pump and a hydraulic control valve.
The present invention further relates to a hydraulic controller for a transmission which comprises an oil pump whose pumping action is generated by rotating an inner rotor (including an inner gear) that meshes with an outer rotor (including an outer gear), the inner rotor being positioned inside the internal circumference of the outer rotor. Such an oil pump can be, for example, a trochoidal pump or an internal gear pump.
For hydraulically executing the shift control of a transmission, various types of hydraulic controller have been in use, and hydraulic controllers are incorporated in transmissions for hydraulic shift control. Such a hydraulic controller comprises an oil pump and hydraulic control valves, which are provided in the transmission housing. Various ways to incorporate such hydraulic elements in the transmission housing have been also known. For example, Japanese Laid-Open Patent Publication No. H03(1991)-121370 discloses a hydraulic controller in which hydraulic control valves are placed on the rear end of the transmission housing with a side cover covering these hydraulic control valves while an oil pump is placed at the front of the transmission housing.
In such a hydraulic controller, because the oil pump is positioned away from the hydraulic control valves in the transmission housing, it is necessary to form oil passages in the housing to supply oil from the oil pump to the hydraulic control valves. It is important to lay out the passages without complicating the arrangement. If the arrangement becomes complicated, then the length of oil passages tends to become longer. This problem can result in an increase in the flow resistance of oil passages, leading to an appreciable pressure loss, which reduces the efficiency of the pump.
There is an arrangement in which valve bodies constitute a pump casing wherein an outer rotor, an inner rotor, etc. are placed. However, the valve bodies are made of an aluminum material for weight saving while the oil pump is made of an iron material for strength. If valve bodies are to constitute a pump casing, then a question is what material it should be made of. For example, if valve bodies are made of an aluminum material, then the pump casing formed with these valve bodies may lack sufficient strength. In addition, if a rotor member made of an iron material is to be used in a pump casing made of an aluminum material, then the clearance between them in assembled condition must be larger than when both parts are made of an identical material. Without such a precaution, the pump will experience a reduction in volumetric efficiency. On the other hand, if the valve bodies are made of an iron material, then these problems will be solved, but this will contribute to the total weight of the transmission.
By the way, oil pumps of the type described above include, for example, trochoidal pumps and internal gear pumps. In such a pump, an inner rotor (including an inner gear) is positioned inside the internal circumference of an outer rotor (including an outer gear), and pumping action is generated by rotating the inner rotor, which meshes with the outer rotor.
Such an oil pump is mounted, for example, on an input shaft of a transmission and driven by the rotation of an engine to produce hydraulic pressure for shift control, etc. The pump as a unit does not have its own drive shaft because it is intended to be mounted on the input shaft of the transmission or a drive shaft which is connected directly with the output shaft of the engine. Therefore, the pump as a unit in preassembled condition has only an inner rotor and an outer rotor in a pump casing. The outer rotor is positioned (centered) and retained in the rotor-accommodating room of the pump casing while the inner rotor is placed, without any restriction, in the outer rotor.
When the pump is mounted on the drive shaft, the drive shaft fits into a bore provided through the inner rotor. As mentioned above, because the inner rotor is free in the outer rotor and not centered, it is difficult to insert and fit the drive shaft into the bore of the inner rotor in assembly process. To solve this problem, Japanese Utility-Model Publication No. 2589791 discloses an arrangement which makes the fitting of the drive shaft simple. In this arrangement, a taper is provided at an end face of the bore of the inner rotor (inner gear), and also a taper is provided at an end face of a cylindrical bush-like bearing, which is provided in the transmission housing to support the drive shaft, rotatably When the tapered part of the bearing is inserted into the tapered part of the bore of the inner rotor, the inner rotor is mounted and centered in the housing. In this condition, the drive shaft is fit into the bore of the inner rotor, which has been already centered in the housing.
However, this arrangement is disadvantageous because it limits the order of assembly for mounting the components of the pump in the transmission housing. In the order of assembly, the cylindrical bearing must be placed in the housing first, on which bearing, the inner rotor is mounted for centering. Also, this arrangement does not allow for the pump to be assembled independently as a unit. This is a problem because the components of the pump must be managed as independent parts in assembly processes until the final assembly of the pump to the transmission. Another problem is that as the pump is not assembled as a unit, the performance of the pump cannot be tested as a unit.
Japanese Laid-Open Utility-Model Publication No. S58(1983)-84387 discloses an arrangement for the centering of the inner rotor. In this arrangement, the inner rotor is provided with a cylindrical guide portion which protrudes from one end face thereof, and this guide portion is inserted into a guide-receiving bore formed in the casing. By this arrangement, the inner rotor of the pump can be centered as a unit, so the pump can be easily mounted on the drive shaft. However, in this case, as the inner rotor is provided with a cylindrical guide portion, not only the machining of the guide portion is an extra process, but also the grinding of the end face of the inner rotor is made difficult because of the existence of this guide portion.
It is an object of the present invention to provide a hydraulic controller which comprises an oil pump and hydraulic control valves placed next to one another in a compact manner.
It is another object of the present invention to provide a hydraulic controller which comprises a shift control valve whose valve body is made of an aluminum material and an oil pump made of an iron material.
It is yet another object of the present invention to provide a hydraulic controller which comprises an oil pump whose inner rotor is centered even while the pump exits as a preassembled unit. The present invention provides this centering without forming a protrusion like the above mentioned guide portion provided on an end face of the inner rotor.
A hydraulic controller according to the present invention comprises a valve body for a hydraulic control valve (for example, the valve body of the first hydraulic control valve 60 described in the following embodiment), an oil pump and a pump drive shaft (for example, the input shaft 1 of a transmission described in the embodiment). The valve body is mounted on an internal wall (for example, the end face S1 of the first housing unit H1 in the following embodiment) of a transmission housing (the first housing unit H1), the oil pump is mounted on the valve body, and the pump drive shaft is provided rotatably in the transmission housing. In this hydraulic controller, the oil pump comprises a pump casing, which is mounted to the valve body, an outer rotor and an inner rotor, both of which are provided in the pump casing. The pump drive shaft is inserted into the pump casing and fit into the inner rotor, so that the inner rotor is rotated and driven by the pump drive shaft. Furthermore, the oil pump sucks oil from an oil tank, which is formed at the bottom of the transmission housing, and supplies it through the mounting surface to the valve body into the valve body of the hydraulic control valve.
In the construction of the hydraulic controller, the oil pump is mounted directly on the valve body to make the supply of oil to the control valve simple. As a result, the oil pump is operated efficiently with little pressure loss. Moreover, as the oil pump is mounted on the valve body, which is mounted on the transmission housing, the assembly of the oil pump is simple, and the hydraulic controller as a whole is compact.
It is preferable that the pump casing, the outer rotor and the inner rotor be made of an iron material and that the valve body be made of an aluminum material. In this way, the oil pump is made not only with sufficient strength but also with high volumetric efficiency without being affected from thermal expansion. Also, the valve body, which is comparatively larger than the pump casing, is made of an aluminum material for saving weight. As a result, the hydraulic controller as a whole is light and compact.
It is also preferable that a pump-accommodating concave be formed in the internal wall of the transmission housing. With this arrangement, when the valve body of the hydraulic control valve is mounted on the internal wall, the oil pump, which is already mounted on the valve body, will be preferably accommodated in the pump-accommodating concave. As the oil pump is accommodated inside the internal wall of the transmission housing, the hydraulic controller is made more compact.
Such an oil pump used for a hydraulic controller according to the present invention comprises a pump casing, an outer rotor, an inner rotor and a pump cover. The pump casing has a rotor-accommodating room (for example, the space defined by the rotor-accommodating hollow 51a described in the following embodiment), in which the outer rotor is accommodated and held rotatably. The inner rotor is positioned in the outer rotor, and the pump cover is mounted on the pump casing, covering the rotor-accommodating room, where the outer rotor and the inner rotor are positioned. A pump drive shaft (for example, the input shaft 1 of a transmission described in the following embodiment), which is inserted through an insertion bore (for example, the fitting recess 53b and the through hole 54e in the following embodiment) formed through the pump casing and the pump cover, fits into a bore provided in the inner rotor, so that the pump drive shaft can rotate and drive the inner rotor. In this case, the pump drive shaft is held rotatably with a bearing, which is retained in the insertion bore formed in the pump casing. Because the internally extending axial end of the bearing protrudes into the rotor-accommodating room, it is received in a fitting recess formed on the end face of the inner rotor that faces the pump casing. As a result, the inner rotor is centered and held by the bearing.
In this arrangement, as the outer rotor and the inner rotor are positioned in the rotor-accommodating room, which is provided in the pump casing, the internally extending axial end of the bearing, which is retained in the insertion bore of the pump casing, protrudes into the rotor-accommodating room and is received in the fitting recess of the inner rotor. In this way, the inner rotor is centered and held by the internal end of the bearing. As a result, the oil pump as an independent unit, which is assembled with the outer rotor and the inner rotor mounted in the rotor-accommodating room and covered by the pump cover (i.e., in the condition before a pump drive shaft is inserted), has the inner rotor already centered. Therefore, it is easy to mount the oil pump, in which process, the drive shaft for the pump is inserted through the insertion bore, which is formed through the pump casing and the pump cover, and fit into the bore of the inner rotor.
It is preferable that the pump casing be formed with at least a suction port or a delivery port positioned around the insertion bore, where the bearing is to be retained. The pump casing needs to be formed with a sufficient thickness in the axial direction especially at the part where the bearing is to be held. Therefore, the suction port and the delivery port are formed in this axially thickened part to exploit the space effectively in the pump casing.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.